EP0695532A2 - Circular anastomosis device - Google Patents

Abstract

A surgical instrument for performing a circular anastomosis is disclosed. The instrument has preferred features which include a tissue piercing tip 354 with a protective cover 358 and various structures for controlling staple formation.

Description

BACKGROUND1.Field of the Invention
• This invention relates to a surgical fastener applying instrument. More particularly, this invention relates to an arrangement for a circular anastomosis surgical stapling instrument.
2.Description of the Related Art
• Various types of surgical fastener applying instruments have been known for the application of surgical fasteners to tissue. For example, it has been known to use various types of surgical staplers in gastric and esophageal surgery in both classic or modified gastric reconstructions performed end-to-end, end-to-side or side-to-side. In many cases, instruments, such as described in U.S. Patent No. 4,603,693, have been used where an anvil assembly mounted on the end of a center rod can be manipulated relative to a staple assembly on the end of a tubular housing of the instrument. In instruments of this nature, the center rod is connected with a mechanism, for example, which employs a wing nut at the proximal end of the instrument, so that the rod can be moved back and forth independently of the staple assembly so as to adjust the anvil assembly relative to the staple assembly. Likewise, a pusher tube is mounted within the instrument for movement via a handle mechanism so as to cause a firing of the staples from the staple assembly towards the anvil assembly.
• In some instruments, such as described in U.S. Patent No. 4,351,466, these stapling instruments have been provided with a pair of handles in order to actuate the pusher tube to cause a firing of the staples. In such cases, each handle has been pivotally mounted so as to be moved toward the other handle during manual squeezing by a surgeon. Each handle also includes a lever arm within the instrument which engages against the pusher tube so as to move the tube in a proximal direction. In most surgical stapling applications, proper staple formation is very important to achieve the desired anastomosis. As such, proper alignment of parts during manufacture and precise mechanisms to control staple formation during use are advantageous.
• Circular stapling instruments have also been provided with safety locks in order to prevent the squeezing together of the handles prematurely. That is, the safety locks have been provided in order to prevent the handles from moving towards each other before a surgeon has manipulated the anvil assembly into position for the firing of the staples. While these instruments have been used safely and effectively for years, it would be advantageous to provide the feature of preventing the anvil member from being able to be moved once a fastener firing safety lock has been released. Also a continuing need exists to develop these types of surgical stapling instruments which require fewer parts and materials to manufacture, thereby reducing costs of production and requiring less labor to assemble the parts. Additionally, if the instruments are disposable, i.e. single use only, use of less materials is desirable to decrease the amount of medical waste generated during a surgical procedure.
• In some applications of circular anastomosis devices, tissue must be pierced in order to connect the stapling mechanism and anvil member. U.S. Patent No. 5,119,983 discloses a removable tip portion to facilitate this procedure. After piercing tissue, the tip portion is removed and the anvil is joined to the stapler. U.S. Patent No. 5,104,025 discloses a tip portion for piercing tissue and a rigid sleeve for protecting the tip portion. The entire rigid sleeve reciprocates relative to the tip portion by means of a spring to expose the tip portion. The spring also serves to secure the sleeve to the stapling head portion of the instrument. While the removable tip embodiment of U.S. Patent No. 5,119,983 has been used successfully for years, there is always a need for more cost efficient devices.
SUMMARY
• The present invention provides a surgical fastener applying instrument which includes a novel anvil lockout mechanism which works in cooperation with the safety release mechanism for the fastener firing member. The instrument of the present invention is lightweight and easy to manufacture. It requires fewer component parts than similar available instruments and, therefore, is less costly to produce.
• The surgical instrument includes a housing having proximal and distal end portions, a shaft extending from the housing distal end portion, the shaft having proximal and distal end portions, a fastener carrying cartridge positioned at the shaft distal end portion, the cartridge having a plurality of fasteners disposed therein, a fastener firing member operatively associated with the fastener carrying cartridge, at least one lever extending from the housing, the lever being adapted to move the fastener firing member to expel the fasteners from the cartridge, an anvil member disposed opposite the cartridge, an elongated member operatively associated with the anvil member for moving the anvil member relative to the cartridge, and locking means disposed within the housing for locking the elongated member, and, therefore the anvil member, the locking means being movable between at least a first position and a second position such that when the locking means is in the first position the elongated member is movable and when the locking means is in the second position the elongated member is prevented from moving.
• In a preferred embodiment the locking means is operatively associated with a safety mechanism for preventing movement of the at least one lever, the safety mechanism being movable between at least a first position and a second position.
• In another preferred embodiment, a mechanism for adjusting the distance between the fastener head assembly and the instrument housing is disclosed. This mechanism permits accurate calibration of the instrument after assembly, thereby obviating the need to closely monitor calibration during assembly and the potential need to rework assembled product.
• Another preferred embodiment includes a tip portion adapted to pierce tissue associated with a movable anvil retaining member. A deformable protective member is also disclosed to prevent inadvertent contact between the tip portion and tissue.
• Yet another preferred embodiment includes structure disposed in the fastener head assembly for ensuring proper staple formation. The structure ensures the staples do not become over crimped against the anvil.
BRIEF DESCRIPTION OF THE DRAWINGS
• Preferred embodiments of the invention are described hereinbelow with reference to the drawings wherein:
• Fig. 1 is a perspective view of an instrument constructed according to the present invention for applying surgical fasteners to tissue;
• Fig. 2 is an exploded perspective view of an instrument in accordance with the present invention;
• Fig. 3 is a top plan view of the fastener firing member of the present invention;
• Fig. 4 is a side plan view of the fastener firing member;
• Fig. 5 is an end view of the fastener firing member;
• Fig. 6 is a top plan view of the elongated member for moving the anvil of the present invention relative to the stapling cartridge;
• Fig. 7 is a side plan view of the elongated member of Fig. 6;
• Fig. 8 is a cross-sectional view taken along section line 8-8 of Fig. 6;
• Fig. 9 is a cross-sectional view taken along section line 9-9 of Fig. 7;
• Fig. 10 is a plan view of the instrument showing the lever members in the unfired position;
• Fig. 11 is a cross-sectional view taken along section line 11-11 of Fig. 10;
• Fig. 11A is an enlarged view of the area indicated in Fig. 11;
• Fig. 12 is a plan view of the instrument showing the lever members in the fired position;
• Fig. 13 is a cross-sectional view taken along section line 13-13 of Fig. 12;
• Fig. 13A is an enlarged view of the area indicated on Fig. 13;
• Fig. 14 is a perspective view of another embodiment of the instrument constructed according to the present invention for applying surgical fasteners to tissue;
• Fig. 15 is an exploded perspective view of the instrument of Fig. 14;
• Fig. 16 is an enlarged, partially cut away cross-section view of the insert guide of the instrument of Fig. 14;
• Fig. 17 is an enlarged exploded view of the distal of the instrument of Fig. 14; and
• Fig. 18 is an enlarged view of the distal end of the elongate member and sharp tip of the instrument of Fig. 14.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
• Referring now in specific detail to the drawings, in which like reference numerals identify similar or identical elements throughout the several views, and initially to Fig. 1, which shows one embodiment of the surgical instrument for applying a circular array of fasteners of the present invention illustrated in perspective view asinstrument 10.Instrument 10 includeselongate body portion 12 and handlesection 14.Handle section 14 includesanvil adjustment member 16, lever lockout orsafety member 18 and fastener firing levers 20.Fastener head portion 22 andanvil member 24 are disposed at the distal end ofbody portion 12. Except where noted otherwise, the materials utilized in the components of the surgical instrument of the present invention generally include such materials as polycarbonate for housing sections and related components, and stainless steel for such components which transmit forces. One preferred polycarbonate material is LEXAN® brand polycarbonate available from General Electric Company. However, equivalent alternative materials will readily come to the mind of those skilled in the art.
• Referring now to Fig. 2, the various components ofinstrument 10 are shown in exploded view.Instrument 10 includes body orhousing half sections 12a and 12b which are preferably molded and joined together by suitable fastening means such asrivets 28, or the like. To control axial movement ofanvil member 24, elongatedmember 30 is slidably mounted withinbody portion 12, preferably by being securely mounted tohelical cam member 32 by any suitable means such as, for example, welding or the like.Helical cam member 32 is slidably mounted withinanvil adjustment member 16 by way of bushing 34 which is securely mounted inopen end 36 ofanvil adjustment member 16.Friction member 93 is disposed adjacentanvil adjustment member 16 to prevent relatively free rotation of the anvil adjustment member. In a preferred embodiment, both the mounting ofbushing 34 and the camming ofhelical cam 32 is accomplished bycompound pin 38 which hascentral portion 38a and extendingportions 38b and 38c which are of reduced diameter.Portions 38a and 38b are press fitted intobores 40 and 42, respectively, located on bushing 34 andanvil adjustment member 16, respectively. Lower extendingportion 38c serves as a camming pin and fits within the helical groove formed on the surface ofhelical cam 32. Anvilapproximation indicator member 46 has extendedportion 48 and is press fitted into proximal portion 50 ofhelical cam 32.Cap 51 is attached toproximal end 52 of anvilapproximation indicator member 46.Cap 51 is preferably a colored piece which is easily visible throughopening 54 formed near the proximal end ofanvil adjustment member 16 to provide indication to the user when the anvil member is in the proper position for firing of the instrument. The distal end ofelongated member 30 is provided with means to retainanvil member 24, which will be described in more detail below.
• The fastener firing mechanism ofinstrument 10 includesfastener firing member 56 which is slidably mounted withinbody portion 12 preferably such thatfastener firing member 56 is disposed around elongatedmember 30.Fastener firing member 56 is preferably biased in a proximal direction by suitable biasing means such asspring 58. Fastener firing levers 20 are pivotably mounted tobody portion 12 and have extendedportions 60 which cross over each other in scissor-like fashion.Bearing block 62 is mounted onfastener firing member 56, for example, being held betweenflexible finger portions 64 and raisedportions 66 which are formed in the side walls offastener firing member 56, as best illustrated in Figs. 3 and 4.Fastener firing member 56 has bearing surfaces such astabs 68 formed at the distal portion which serve to urge a pusher member withinfastener head portion 22 in a distal direction in order to ejectsurgical fasteners 69, such as stainless steel or titanium staples, fromfastener head portion 22.
• Also disposed oninstrument 10 arelever lockout member 18 and elongatemember lockout member 70.Lever lockout member 18 is preferably spring biased to the locked out position byspring 67 inslot 91. Each of these lockout members are preferably mounted oninstrument 10 in such a manner that they are fixed relative to each other and upon pivoting oflever lockout member 18, elongatemember lockout member 70 also pivots. With reference to Figs. 11A and 13A, elongatemember lockout member 70 hasshoulder portions 73 and 75 formed therein as well as inwardly extendingtab 79. The function of each of these portions of elongatemember lockout member 70 will be described in further detail later herein.
• Referring now to Figs. 3-9, the structural and functional details offastener firing member 56 andelongated member 30 will now be described in detail. In Figs. 3-5,fastener firing member 56 is shown as preferably being a generally U-shaped member formed from material which can transmit forces effectively and reliably such as stainless steel.Fastener firing member 56 hasside walls 72 and 74 which are connected byweb 76. To fitfastener firing member 56 within the curved section ofbody portion 12,fastener firing member 56 has extended portions orflexible bands 72a and 74a which are preferably formed integrally withwalls 72 and 74, respectively.Band 72a is shorter than band 74a. The difference in the length of the two bands corresponds to the amount of curvature ofbody portion 12 so that whenfastener firing member 56 is mounted inbody portion 12, the surfaces oftabs 68 form a plane parallel with the surface of the fastener pusher member (not shown).
• Referring to Figs. 6-9, elongatedmember 30 is shown as a U-shaped member, similar tofastener firing member 56.Elongated member 30 hasside walls 78 and 80 which are joined byweb 82. However, the cross-section dimensions ofelongated member 30 are preferably such thatelongated member 30 readily fits withinfastener firing member 56. This arrangement is desirable so thatelongated member 30 andfastener firing member 56 can slide independent of each other. As withfastener firing member 56, elongatedmember 30 must also be formed to fit within the curved contour ofbody portion 12. To accomplish this curvature, elongatedmember 30 has extended portions orflexible bands 78a and 80a which are preferably formed integrally withwalls 78 and 80, respectively. Similar to the construction offastener firing member 56,bands 78a and 80a ofelongated member 30 are of different length.Elongated member 30 terminates at a distal end in a pair of opposedanvil retaining portions 84 and 86. Preferably, structure can be provided within body portion 12 (see 320 in Fig. 15) that serves to retain the side walls and bands of both elongatedmember 30 andfastener firing member 56. Such structure can be of unitary construction and have grooves to direct longitudinal movement of the channels and bands. Additionally, one or more seals (see 326a dn 326b in Fig. 15) can be disposed withinbody portion 12 to prevent the flow of gases therethrough.
• To facilitate retaininganvil member 24, and in particular, the anvil shaft therein,anvil retaining portions 84 and 86 are preferably semi-circular in shape as best illustrated in the cross-section view of Fig. 8. To assist in retention ofanvil 24,anvil retaining portions 84 and 86 are provided withflexible finger portions 88 and 90, respectively, each of which have a raised portion formed thereon, such as camming and retainingportions 92 and 94, respectively. Camming surfaces 96 and 98 formed by camming and retainingportions 92 and 94, respectively serve to camflexible finger portions 88 and 90 radially outward upon insertion of the anvil into the distal end ofinstrument 10. Referring temporarily back to Fig. 2, onceannular groove portion 100 ofanvil shaft 102 passes between retainingportions 84 and 86,flexible finger portions 88 and 90 return toward their initial or at rest state so that retainingportions 92 and 94 seat inannular groove 100.
• In a preferred embodiment,extended portions 78a and 80a ofelongated member 30 are preferably bent until the ends ofanvil retaining portions 84 and 86 are aligned and are then permanently joined together (as shown in Fig. 2), by suitable bonding techniques, such as, by welding.
• At the proximal end ofelongated member 30, cut outportion 83 is formed to receive elongatemember lockout member 70 when elongated member is properly positioned for firing the staples ofinstrument 10. As best illustrated in Figs. 6 and 7,cutout portion 83 is preferably formed through most ofweb 82 and continues partially upside wall 80.
• The basic steps of operation are set forth in several patents, such as U.S. Patents 4,576,167 issued to Noiles, 5,005,749 issued to Aranyi, and 5,119,983 to Green et al. the contents of each of these references are hereby incorporated by reference.
• With reference to the instrument of the present invention, the user positions the tissue to be joined betweenanvil 24 andfastener head portion 22.Anvil adjustment member 16 is rotated to move elongatedmember 30 andanvil 24 proximally until the user seesapproximation indicator 46 appear in opening 54 ofanvil adjustment member 16. During this step,elongate member 30 acts as a tension member as it pullsanvil 24 into position adjacentfastener head portion 22. Prior to alignment of cut out 83 inelongate member 30 andextended portion 79 ofelongate member lockout 70,lockout 70 is prevented from pivoting by contact betweenextended portion 79 andelongate member 30. When cut out 83 is positioned adjacentextended portion 79 ofelongate member lockout 70, as further described below,lever lockout member 18 andelongate member lockout 70 are able to be pivoted by depressing, usually with the thumb, onlever lockout member 18.Members 18 and 70 can be interconnected by any suitable means, i.e., protrusion from one member entering a recess in the other. Oncelever lockout member 18 is pivoted by the user, fastener firing levers 20 are depressed to urgefastener firing member 56 in a distal direction. This motion is accomplished by the camming effect ofextended portions 60 of fastener firing levers 20 on bearingblock 62 the distal movement offastener firing member 56 urges fastener pusher members to ejectfasteners 69 fromfastener head portion 22. During this step,fastener firing member 56 acts as a compression member as it ejectsfasteners 69.
• With the above operational description ofinstrument 10 as a general base of the overall operation, the operation ofelongate member lockout 70 will now be described in detail with reference to Figs. 10-13. Once the user hasinstrument 10 inserted and the tissue to be joined is properly situated about the distal end of the instrument,anvil 24 is approximated to its proper position by rotation ofanvil adjustment member 16,instrument 10 is positioned for firing, as shown in Fig. 10. In that position, however,fastener firing member 56 is still blocked from movement due tolever lockout member 18 still being oriented in the "safety on" position,i.e., lever lockingextended portions 104 and 106 (Fig. 2) are aligned with the structure oflevers 20 so that they cannot be depressed. Pivoting oflever lockout member 18 is prevented when elongatedmember 30 is out of the desired approximation range for firing the staples.
• With reference to Figs. 2-7, 11 and 13, prevention of the ability to pivotlever lockout member 18 is accomplished by the relative position ofelongated member 30 and thus the approximation ofanvil 24. Whenanvil 24 is not properly approximated,side wall 80 andweb 82 ofelongated member 30 preventextended portion 79 ofelongate member lockout 70 from moving further inward (Fig. 11). However, once elongatedmember 30 is properly positioned,i.e., cut out 83 is aligned withextended portion 79 ofelongate member lockout 70, thenlever lockout member 18 which is fixedly secured to elongatemember lockout member 70, can be pivoted, as shown in Fig. 13. Whenlockout 70 is pivoted,shoulder portions 73 and 75 oflockout 70 are moved out ofnotches 77 of fastener firing member 56 (Figs. 3 and 4). This enables fastener firing levers 20 to be pivoted toward each other as shown in Fig. 12, thereby movingfastener firing member 56 distally and ejectingfasteners 69 fromfastener head portion 22. As can be seen in Figs. 13 and 13A oncelever lockout 18, and elongatemember lockout 70 are pivoted by the user, inwardly extendingportion 79 oflockout 70 enters into cut out 83 (Figs. 6 and 7) and blocks elongatedmember 30 from movement in either a proximal or distal direction.
• Referring now to Figs. 14-18, another embodiment of the present invention shown asinstrument 210 will now be described. For purposes of clarity, components of the instrument of Figs. 14-18 which are similar or identical to those of the embodiment for Figs. 1-13 have been labeled by adding 200 to the reference numerals of the earlier embodiment. For example,anvil shaft 102 of Fig. 2 corresponds toanvil shaft 302 of Fig. 15.
• Referring now to Fig. 14 in conjunction with Fig. 15,instrument 210 includesinsert guide 320 which is preferably molded of a polycarbonate material such as LEXAN® available from the General Electric Company.Insert guide 320 is preferably molded to conform to the curvature ofhousing half sections 212a and 212b so as to provide structural support forelongate member 230 andfastener firing member 256. Referring temporarily to Fig. 16,insert guide 320 is illustrated in a partially cut away section to show the guide tracks which receiveelongate member 230 andfastener firing member 256 therein. Specifically, outer guide tracks 322 are molded to receivesidewalls 272 and 274 therein and inner guide tracks 324 are formed to receiveside walls 78 and 80 ofelongate member 30 therein.Insert guide 320 thereby provides structural support upon longitudinal motion of eitherelongate member 230 orfastener firing member 256, particularly at the point of curvature thereof.Insert guide 320 effectively reduces possible force transmission losses upon operation ofinstrument 210.
• In order to provide an internal seal inbody portion 212, sealhalf sections 326a and 326b are formed to fit around notches formed oninsert guide 320.Seal half sections 326a and 326b are preferably molded of a hard rubber material which is molded to conform with the inner dimensions ofhousing half sections 212a and 212b. Additionally, sealhalf sections 326a and 326b are molded to fit overelongate member 230 andfastener firing member 256 so as to form a seal between the internal section of theinstrument 210 which is distal of theseal half sections 326a and 326b and the internal portions ofinstrument 210 which are proximal ofseal half sections 326a and 326b so as to inhibit the passage of gases thereby.
• Referring now to figure 15 in conjunction with Fig. 17, additional features of the present invention are illustrated therein which will now be described. An adjusting member such ascollar 328 is mounted between the distal end ofhousing 212 and the proximal end of fastenerhead portion assembly 222.Collar 328 has ratchetteeth 330 formed on an inner surface thereof at the proximal end. Ratchetteeth 330 cooperate withratchet teeth 332 formed on the distal end ofhousing half sections 212a and 212b. Ratchetteeth 330 and 332 interact to provide for rotational advancement ofcollar 328 in a single direction. Also formed oncollar 328 are cammingsurfaces 334 and 336 which interact withcamming surfaces 338 and 340 formed at the proximal end offastener head portion 222. A purpose ofcollar 328 is to provide for post instrument assembly adjustment of the relative longitudinal positioning of fastenerhead portion assembly 222 with respect to the distal end ofbody portion 212. This adjustment capability is important so thatinstrument 210 may be calibrated to insure the proper positioning ofanvil member 224 whencap 251 of anvilapproximation indicator member 246 is positioned within opening 254 so as to indicate thatinstrument 210 is ready for firing ofsurgical staples 269. Onceinstrument 210 is properly calibrated,collar member 328 may be fixedly secured to the distal end ofbody portion 212 so thatcollar 328 is not permitted to rotate with respect thereto. This attachment may be accomplished by known suitable means such as, for example, bonding and/or by the use of a fastener such as a screw or a pin.
• Another important feature illustrated in Fig. 17 provides protection against over crimping ofsurgical staples 269 upon firing ofinstrument 210. Pusher back 342 is provided with longitudinally extendingportions 344 which are configured to fit inside ofknife ring 346 and are preferably sized to abut against a surface portion, such ascut ring 345, ofanvil 224 upon firing ofinstrument 210. Whenportions 344 of pusher back 342 contact a portion ofanvil 224,pusher fingers 252 are prevented from traveling further, thereby limiting the degree to whichsurgical staples 269 may be crimped againstanvil 224.
• In another feature of the present invention, referring now Fig. 15 in conjunction with Fig. 18,elongate member 230 hastip 354 formed at the distal end to facilitate puncturing of tissue as desired by the user ofinstrument 210.Tip 354 is preferably sharp and formed by known methods such as, for example, grinding with suitable abrasives.Tip 354 is formed such that a hollow passageway oropening 356 is formed which passes longitudinally through the distal end portion ofelongate member 230. Opening 356 onelongate member 230 is preferably sized so that it can receiveshaft 302 ofanvil 224 so thatanvil 224 may be retained by the distal end portion ofelongate member 230 in a similar manner as set forth above forelongate member 30 andanvil 24 for the embodiment of Figs. 1-13. To avoid inadvertent lateral contact with tip 354 a protective cover is provided, such ascover 358 which is preferably formed of a deformable elastomeric material. Cover 358 is provided with raisedportions 360 which correspond tobores 362 formed onelongate member 230 proximal oftip 354. In use, whenelongate member 230 is extended pasthead portion assembly 222,cover 358 deflects upon contact with tissue to exposetip 354. Aftertip 354 and cover 358 pass through the tissue, cover 358 returns to a position which protectstip 354, thereby providing means for preventing inadvertent trauma bytip 354 to surrounding tissue.
• The operation ofinstrument 210 is similar to that ofinstrument 10 except as noted hereinabove. Accordingly, no separate description of the operation ofinstrument 210 will be provided at this point.
• The claims which follow identify embodiment of the invention additional to those described in detail above.

Claims (19)

1. A surgical instrument for applying at least one circular array of fasteners, comprising:
      a housing having proximal and distal end portions;
      an elongate shaft extending from the housing distal end portion, the shaft having proximal and distal end portions;
      a fastener carrying cartridge positioned at the shaft distal end portion;
      an adjusting member operatively associated with the fastener carrying cartridge to adjust the longitudinal positioning of the fastener carrying cartridge relative the distal end of the shaft; and
      an anvil member operatively disposed adjacent the fastener carrying cartridge.
2. A surgical instrument as recited in claim 1, wherein the adjusting member includes at least one camming surface operatively associated with the fastener carrying cartridge.
3. A surgical instrument as recited in claim 2, wherein the fastener carrying cartridge includes at least one camming surface operatively associated with the at least one camming surface of the adjusting member.
4. A surgical instrument as recited in claim 1,2 or 3, wherein the adjusting member is a rotatable collar member.
5. A surgical instrument as recited in claim 4, wherein the collar member includes incremental portions disposed thereon adapted to incrementally facilitate movement of the collar member camming surface upon movement of the collar member relative to the distal end of the elongated shaft.
6. A surgical instrument as recited in claim 5, wherein the incremental portions of the collar member are adapted to facilitate movement of the collar member in a single direction.
7. A surgical instrument as recited in claim 5 or 6, wherein the incremental portions of the collar member include a plurality of ratchet teeth which are operatively associated with at least one tooth portion formed on the elongated shaft.
8. A surgical instrument as recited in any one of the preceding claims, further comprising an elongate anvil retaining member reciprocatingly movable within the fastener carrying cartridge.
9. A surgical instrument as recited in claim 8, wherein the elongate anvil retaining member has a hollow distal portion.
10. A surgical instrument as recited in claim 8, wherein the hollow distal portion forms a sharp tip at a distal end of the retaining member.
11. A surgical instrument for applying at least one circular array of fasteners, comprising:
       a housing having proximal and distal portions;
       an elongate shaft extending from the housing distal portion, the shaft having proximal and distal end portions;
       a fastener carrying cartridge positioned at the shaft distal end portion;
       an elongate anvil retaining member reciprocatingly movable within the fastener carrying cartridge, defining a hollow distal portion forming a tip at a distal end thereof; and
       an anvil member adapted for removable attachment to the elongate anvil retaining member.
12. A surgical instrument as recited in claim 11, further comprising an adjusting member operatively associated with the fastener carrying cartridge to adjust the longitudinal positioning of the fastener carrying cartridge relative the distal end of the shaft.
13. A surgical instrument as recited in any one of claims 8 to 11, further comprising a resilient shield member connected to the elongate anvil retaining member and disposed around the tip.
14. A surgical instrument as recited in claim 13, wherein the resilient shield member is at least partially formed from an elastomeric material.
15. A surgical instrument for applying at least one circular array of fasteners, comprising:
       a housing having proximal and distal end portions;
       an elongate shaft extending from the housing distal end portion, the shaft having proximal and distal end portions;
       a fastener carrying cartridge positioned at the shaft distal end portion, the fastener carrying cartridge including a housing, a plurality of surgical fasteners disposed within the housing, a pusher member operatively associated with the surgical fasteners, a knife member disposed within the housing and a fastener crimping limit member disposed within the housing; and
       an anvil member operatively disposed adjacent the fastener carrying cartridge.
16. A surgical instrument as recited in claim 15, wherein the fastener crimping limit member includes a base having a longitudinal portion extending therefrom which is operatively associated with the anvil member to limit the crimping of the surgical fasteners upon firing of the instrument.
17. A surgical instrument as recited in claim 15, wherein the fastener crimping limit member includes a base having a plurality of longitudinally extending finger portions projecting therefrom which are operatively associated with the anvil member to limit the crimping of the surgical fasteners upon firing of the instrument.
18. A surgical instrument for as recited in claim 15, 16 or 17, further comprising an adjusting member operatively associated with the fastener carrying cartridge to adjust the longitudinal positioning of the fastener carrying cartridge relative the distal end of the shaft.
19. A surgical instrument as recited in claim 15, 16 or 17, further comprising an elongate anvil carrying member reciprocatingly movable within the fastener containing cartridge, defining a hollow distal portion forming a sharp tip at a distal end thereof.

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